In recent years, because of the enhanced audio visual oriented trend, the development of a television receiver capable of displaying the image having a higher resolution has been desired so that the above HDTV can be developed corresponding to this demand. The number of scanning lines of the HDTV system is 1,125 lines, which is 2-fold or more compared with the number of scanning lines of 525 of NTSC system. Moreover, as for the aspect ratio, the ratio of the HDTV system is 9:16 while the one of NTSC system is 3:4. Therefore, according to the HDTV system, the image having a higher resolution and giving the user more feeling of being at a live performance than NTSC system can be displayed.
Although the HDTV has such excellent characteristics, the image according to the HDTV system cannot be displayed on the HDTV television receiver as if a video signal of NTSC system is supplied to the HDTV television receiver as it is. This is because the standards of NTSC system and the HDTV system are different as described above.
Hence, in order to display an image according to the video signal of NTSC system on the HDTV television receiver, the present applicant has proposed a conversion apparatus for converting the video signal of NTSC system into a video signal of the HDTV system (See Japanese Unexamined Patent Publication No. Hei-08-051599). This conversion apparatus extracts the pixel data of blocks (regions) corresponding to a subject pixel of the video signal of the HDTV system from the video signal of NTSC system, determines a class of the above-described subject pixel on the basis of level distribution patterns of the pixel data of these blocks, and generates pixel data of the above-described subject pixel corresponding to the class.
In the above-described conversion apparatus, however, the resolution of an image according to the video signal of the HDTV system is fixed and this fails to adjust the resolution to the desired one corresponding to the image contents or the like as the conventional adjustments for contrast, sharpness and the like.
Moreover, in the above-described conversion apparatus, an image quality of an image formed from the video signal of the HDTV system is fixed and this fails to obtain the image quality to which the respective users prefer. Therefore, the user has been required to separately perform a few kinds of adjustments for contrast, sharpness and the like, which have been troublesome.
Alternatively, as a display device for displaying an image formed from the video signal of the HDTV system obtained from the above-described conversion apparatus, a CRT (cathode-ray tube) display, a liquid crystal display, a plasma display, a projector and the like are used. In the above-described conversion apparatus, a image quality of the image formed from the video signal of the HDTV system is fixed, so that the image quality adaptable for the image display device to be used is not available. Therefore, the user has been required to separately adjust contrast, sharpness and the like by, for example, the image-quality-adjustment-function provided to the image display device so as to obtain the image quality adaptable for the image display device, which have been troublesome.
An object of the present invention is to provide an image signal conversion apparatus and the like that the user can optionally adjust the resolution of an image formed from an output image signal to the desired value. Another object of the present invention is to provide an image signal conversion apparatus and the like whose image quality of an image formed from an output image signal automatically becomes preferred one for the user, and which is capable of making the adjustments by the user for contrast, sharpness and the like unnecessary. Still another object of the present invention is to provide an image signal conversion apparatus and the like whose image quality of the image formed from an output image signal automatically becomes adaptable for the image display device, and which is capable of making the adjustment by the user for contrast, sharpness and the like unnecessary.